Valve continues the trend of revealing new playable campaigns during conventions at PAX 2009 with the debut of the "Dark Carnival" playable campaign for Left 4 Dead 2. For those of you who can't make the coveted indie show this weekend (myself included... /sadness) here's the bundle of images showing the new ICP-friendly chapter and the new "Jockey" special infected character that's waiting to literally ride survivors into harm's way.